1. Field of the Invention
This invention relates to an orbital speed reducer having an improved drive system. More particularly it relates to a drive system for eliminating radial forces on the drive mechanism and thereby increasing the life of the bearing structure and facilitating the repair or interchange of drive motors.
2. Description of the Prior Art
Speed reduction mechanisms making use of epicyclical movements with gear-like rotors having a perimeter defined by an epitrochoid curve have long been known. The magazine Design News in its Aug. 18, 1961 issue describes a single-stage cycloidal cam that forms the basis of a speed reducing mechanism. A similar structure is shown in my U.S. Pat. No. 3,998,112. Corresponding devices were previously known that made use of spur gears. U.S. Pat. No. 2,250,259 to Foote, Jr. describes such a heliocentric unit. Other related mechanisms are described in U.S. Pat. Nos. 3,429,393; 3,144,791; and 3,783,712.
In operation, most of these speed reducing mechanisms generate radial forces on the drive shaft or its bearings that increases wear, requires stronger drive shafts and associated mechanisms, and makes necessary at least two spaced bearing supports for the drive shaft. To eliminate or limit these radial forces, some of the prior art devices are constructed with substantial tolerances beween the cycloidal cam and the associated rollers or, in a gear type unit, between the teeth of the sun and planet gears. Such tolerances inevitably result in backlash that renders the unit unsatisfactory for precision motion control applications.